<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    #box {
      width: 300px;
      height: 300px;
      margin: 50px auto;
      background-color: rgb(117, 91, 61);
    }
    #box2 {
      width: 300px;
      height: 300px;
      margin: 20px auto;
      background-color: rgb(97, 117, 61);
    }
    #box3 {
      width: 300px;
      height: 300px;
      margin: 20px auto;
      background-color: rgb(231, 112, 33);
    }
  </style>
</head>

<body>
  <div id="app">
    <ul>
      <li v-for="item in arr">
        {{ item }}
      </li>
    </ul>
    <hr>
    <ul>
      <li v-for="(item, index) in arr">
        {{item}}
        =>
        {{index}}
      </li>
    </ul>
    <hr>
    <ul>
      <li v-for="item in json">
        {{item}}
      </li>
    </ul>
    <hr>
    <ul>
      <li v-for="(item, key) in json">
        {{ item }}
        =>
        {{ key }}
      </li>
    </ul>
    <hr>
    <ul>
      <li v-for="(item, key, index) in json">
        {{ item }}
        =>
        {{ key }}
        =>
        {{ index }}
      </li>
    </ul>
  </div>
  <script src="./vue.js"></script>
  <script>
    const vm = new Vue({
      el: '#app',
      data: {
        arr: ['a','b','c','d'],
        json:{
          a: 10,
          b: 20,
          c: 30,
          d: 40
        }
      }
    })
  </script>
</body>

</html>